1. Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor light-emitting device, characterized in the method for forming a p-cladding layer.
2. Background Art
Hitherto, in the Group III nitride semiconductor light-emitting device, a p-cladding layer doped with Mg has been formed between a light-emitting layer and a p-contact layer to prevent electrons from leaking over the light-emitting layer to the side of the p-contact layer, thus electrons has been confined in the light-emitting layer.
In the crystal growth of the p-cladding layer, Mg is gradually incorporated in the crystal since the supply of raw material was started. Mg is not immediately incorporated in the crystal at a target concentration (refer to Japanese Patent Application Laid-Open (kokai) No. 2002-198314, particularly FIG. 5). When the p-cladding layer is formed at a constant supply amount of Mg dopant gas, Mg concentration distribution is formed such that the Mg concentration is low in the vicinity of the light-emitting layer side of the p-cladding layer, and gradually increases from the light-emitting layer side toward the p-contact layer side (refer to FIG. 7). Such Mg concentration distribution causes uneven carrier distribution in the p-cladding layer. The uneven carrier distribution affects the hole injection into the light-emitting layer, thereby adversely affecting the device characteristic such as light emission performance. Moreover, since the Mg concentration is high on the p-contact layer side of the p-cladding layer, crystal defects might occur due to overdoping.
A technique relating to control of Mg concentration and Mg supply amount is disclosed, for example, in Japanese Patent Application Laid-Open (kokai) Nos. 2006-313890 and 2009-164489.
Japanese Patent Application Laid-Open (kokai) No. 2006-313890 discloses that after Group III nitride semiconductor doped with Mg is grown in the atmosphere in which an amount of hydrogen is greater than that of nitrogen in the carrier gas, the supply of the Group III raw material gas is stopped, and Group III nitride semiconductor doped with Mg is regrown in the atmosphere in which an amount of nitrogen is greater than that of hydrogen in the carrier gas. It is disclosed that the Mg concentration is steeply increased in the Group III nitride semiconductor after than before regrowth.
Japanese Patent Application Laid-Open (kokai) No. 2009-164489 discloses that a low-resistance p-type superlattice structure in which AlGaN and GaN are alternately deposited, can be formed by stopping the supply of Mg raw material gas when forming AlGaN and supplying the Mg raw material gas for a shorter time than the GaN growth time when growing GaN.
As mentioned above, the conventional method for producing the p-cladding layer had a problem that the Mg concentration distribution is uneven in the p-cladding layer, thereby adversely affecting the device characteristic.
Japanese Patent Application Laid-Open (kokai) No. 2002-198314 discloses that such uneven Mg concentration distribution is formed. However, there is no description and suggestion about the method to eliminate such unevenness.
Japanese Patent Application Laid-Open (kokai) Nos. 2006-313890 and 2009-164489 do not disclose and suggest such uneven Mg concentration distribution and its elimination method.